Chaps getting the cossie ready for its MOT but keep getting a misfire this only happens if its stationary for a while and the fan kicks in, after this it labours and misses all the time until you switch it off and let it cool for a while.
if you are just driving it runs fine any ideas as what the problem could be?

Cheers
Martin

 

Let me guess, you are running a CONE air filter ?
It sounds as though it is running rich, whilst not normally a problem, when the fans kick in and the car is stationary the cone gets flooded with hot air, which has less oxygen, the effect is the fuel mixture gets richer, you can watch this effect on the MOT gas anylyser as well, you'll see it plain as day.
tabetha

 

Cheers for the reply tabetha!
Would this still cause the misfire even when you are moving again and getting fresh air? As once its started it continues until you switch off and let cool for a while then its ok again!

Cheers
Martin

 

I've run a cone filter ever since I bought my cossie and I've never had an an issue like that so cant see that being the problem tbh.